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Chapter 7

PSYB01 Chapter 7

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University of Toronto Scarborough
David Nussbaum

RESEARCH METHODS IN PSYCHOLOGY Chapter 7: True Experiments II – Multifactorial Designs Substantive Theme: Social and Emotional Influences on Thinking and Perceiving  Paul Erkman shows that emotions can be covertly induced and reliably manipulated by specific facial contractions  The emotional salience of the human face reflects an intricate interactions among distinct features of the face  Factorial Designs are complex experimental designs are used when researchers seek to manipulate two or more independent variables at the same time. They are more realistic because they allow the examination of how independent variables interact with each other. They are more efficient because you can combine experiments into one  The term multifactorial is used for experiments that vary two or more independent variables and provide direct tests of the main effects of each independent variable as well as the interaction effects between and among the independent variables Multifactorial Designs  In a multifactorial experiment, an altogether new independent variable is devised and incorporated into the research design o i.e., two independent variables: mood induction, with two levels, happy or sad, and cognitive exercise, also with two levels, verbal or visual  Qualitatively different  Mood induction (emotion) might influence cognitive exercises (thinking) and whether a particular mood state might be better for performing a particular cognitive exercise  Single-factor experiments must incorporate one and only one independent variable with two or more levels  Each independent variable can be studied either between subjects or within subjects o i.e., Between-subjects: four groups of research participants, each randomly assigned to one of the four experimental conditions: (1) happy mood/verbal; (2) happy mood/visual; (3) sad mood/verbal; and (4) sad mood/visual. o i.e., Within-subjects: all participants would be run through each of the four experimental conditions  Multifactorial designs provide a more realistic model of rich psychological phenomena. It offers an economical and efficient design to evaluate and test the separate and joint influences of one or more independent variables on the dependent variable o i.e., mood influences performance in different ways depending on the cognitive task Notations and Terms  Factorial experiments are typically designated or identified by a numbering notation  2x2 Factorial Design has two independent variables, with two levels or values. The number of numbers tells how many factors or independent variables there are, and the number values tell us how many levels of the independent variables RESEARCH METHODS IN PSYCHOLOGY o i.e., a 3x4 factorial design indicates two independent variables, one with 3 levels, and the other with 4 levels. These levels are combined to make a total of 12 levels or treatments Theory and Examination  Theory provides us with the conceptual framework for how particular psychological phenomena might work in real life o i.e., theories of embodied cognition can be used as a conceptual model for us to understand how we experience, perceive, and communicate emotional information  Theory guides how an experiment is designed, how independent variables are developed and manipulated, how dependent variables are measured, and what specific hypotheses are tested A Complex Within-Subjects Experiment  According to Reginald B. Adams and Robert E. Kleck, eye-gaze direction and facial expressions can each be understood in terms of approach-avoidance motivation o both can share informational value as signals of approach, propelling behavior forward, setting the stage for direct expression, confrontation or “fight;” conversely, they may fuel avoidance, triggering inhibition, culminating in “flight” from negative stimuli, of potential danger and threat  Adams and Kleck constructed a theory, which proposes that facial expressions of emotions and gaze direction operate as a social signaling system that governs our basic evolved behavioral tendencies for approach or avoidance  They further reasoned that our fluency in perceiving facial expressions of emotions reflects a dynamic interaction of signals associated with gaze direction and affective displays etched on our visages Decoding Facial Expressions of Emotion  We naturally and automatically perceive facial expressions of emotion holistically as messages. These facial expressions are nonetheless complex stimuli, configurations of more basic elementary features  The eye region of the face is one of the key sources of information for decoding emotional expression  In a brain imaging study, Whalen and colleagues recorded neural activity while participants viewed a series of slides, each with either fearful white eyes or happy white eyes o Found the amygdala of the human brain to be especially sensitive to fearful white eyes but not to happy white eyes  Experimentation often deconstructs complex phenomena such as facial expression of emotions into discrete components o Ekman’s Facial Action Coding System is an example of how seemingly holistic facial displays of specific emotions can be broken down into combinations of facial muscle movements o Whalen and colleagues showed how critical basic features like eye whites influence how we perceive facial expressions of emotion o Adams and Kleck conceptualized perceptions of facial displays of affect as represented by a dynamic interplay of countenance expression and eye gaze RESEARCH METHODS IN PSYCHOLOGY Devising Independent Variables  Adams and Kleck investigated two aspects of the face that they thought would be particularly important for emotional expression: (a) facial muscle contractions that form different emotional expressions, and (b) gaze direction  Their challenge was to devise a way to separate gaze direction and facial expression so that the effects of each on perception could be studied  They formulated two prong-hypotheses: (a) Anger faces with direct gaze would be more readily perceived than anger faces with averted gaze and (b) fear faces with averted gaze would be more readily perceived than fear faces with direct gaze  To test their hypothesis, they had to first create experimental stimuli to construct facial stimuli that varied in expression and gaze direction o They created four types of faces: (1) anger with direct gaze, (2) anger with averted gaze, (3) fear with direct gaze, and (4) fear with averted gaze  Next, they had to organize their four types of faces into an experimental task for participants to perform o The experimental task they constructed had participants view on at a time on a computer monitor a face that had an expression of either anger or fear and a gaze direction of either direct or averted o For each face, participants made a speedy judgment as to whether the face displayed anger or fear by responding via a right or left mouse click  The final step centered on whether to use a within-subjects or a between-subjects manipulation o They opted for a within-subjects design where all participants received all four types of faces allowing for the comparison of participants’ response times in emotional judgment for the four different kinds of faces  With a within-subjects design, individual differences that could figure very prominently in processing emotions are automatically controlled because each participant serves as his or her own control, these individual differences are effectively held constant  Within-subjects designs are more economical than between-subjects designs because fewer participants are needed to perform the experimental task o However, fewer participants require that you collect more observations per participant The 2x2 Design  The 2x2 factorial design produced four combinations of conditions: anger/direct gaze faces; anger/averted gaze faces; fear/direct gaze faces; and fear/averted gaze faces  The dependent variable was response time in milliseconds for judging faces as expressions of either anger or fear  Table 7.1 – page 216 o Looking at the column means shows us that faces with direct gaze were responded to quickly as faces with averted gaze o Less than one millisecond difference between these two conditions tells us that gaze direction by itself had no effect on response times for emotional judgements RESEARCH METHODS IN PSYCHOLOGY o Looking at the row means shows us that anger faces were responded to more quickly than were fear faces Main Effects  In a factorial experiment, the effects of each independent variable on a dependent variable are referred to as the main effect of that independent variable  A main effect can be calculated for each independent variable o Column means tell us the main effect of gaze direction; row means tell use the main effect for type of facial emotional expression  The main effect of gaze direction of the faces did not significantly influence the dependent variable of response time because the values in the column means were nearly identical  The difference of 29.7 milliseconds in type of facial emotional expression was statistically significant, meaning that it was unlikely due to chance. We can therefore conclude the main effect of type of facial expression of emotion did influence the dependent variable of response time Interactions  Before interpreting the main effect of emotional expression, we must first look to see if there is a statistical interaction between the two independent variables o A statistical interaction occurs when the effects of one level of the independent variable depend on the particular level of the other independent variable  Gaze direction decreased response time in judging anger faces but increased response time in judging fear faces. Averted gaze reduced response time in judging fear faces but direct gaze increased response time in judging anger faces o This pattern reflects an interaction between type of emotional expression and gaze direction. o The interaction means that the effect of emotional expression depended on gaze direction of the face Interpreting Results of Multifactorial Designs  Factorial designs provide two distinct sources of information: (1) main effect of each independent variable by itself and (2) any interaction effect of the independent variables o Main effects are statistically independent of interaction effects  To interpret the results generated from a multifactorial 2x2 experiment, begin by looking to see if there is an interaction between the independent variables, and if so, interpret the interaction first, before the main effects  An interaction indicates that any interpretation of a main effect of an independent variable by itself will be misleading because the interaction tells us that the effects of the independent variable depend upon the particular level of the other independent variable  Main effects and interactions are often graphed to help understand and interpret data  Exhibit 7.5 (page 220) plots the interaction of emotion type and gaze direction o Plot the values in each of the four cells of Table 7.1. Each cell value reflects the simple main effect which compares the influence of one level of an independent variable at a given level of another independent variable RESEARCH METHODS IN PSYCHOLOGY o The simple main effects in Table 7.1 reveal a pattern of a classic cross-over interaction – if the lines did not cross over and in fact were parallel, we would conclude that no interaction occurred between the independent variables The 2x2 Logic  The 2x2 design provides a direct test of the main effects of the two independent variables as well as the direct test of the interaction between them  In a 2x2 design, there are eight possible patterns of results for the design used by Adams and Kleck  Experimentalists often use the term additivity to indicate the absense of interaction between independent variables o For exa
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